A biopsy involves removing tissue to find out if you have a disease or the extent of it. The FDA recently approved a less-invasive “liquid” biopsy for a certain form of lung cancer. But the possibilities are far greater.
Highlights from the interview with Dr. Darshan Gandhi, Medical Director of Oncology at Methodist Charlton Medical Center.
What is a liquid biopsy? “Simply checking a blood sample for tumor DNA. So instead of looking at the tumor directly, you’re looking at the DNA that is released when a tumor cell dies, more like an indirect test looking for the tumor. (Previous similar tests helped with prognosis.) Fast forward now, you could make a treatment decision based on this biopsy.”
Why is this test better? "They're looking at some very specific genes that go abnormal, causing the cancer to begin with. And now there is a treatment, a pill called Tarceva. It's a pill or a biologic agent, which not like your traditional chemotherapy, that can be taken by mouth, and can go in the bloodstream, go to the tumor, and directly affect or target this particular gene that is on the cancer cell.
The test is limited to non-small cell lung cancer “There are two different types of lung cancer. If you just look at how the cancer behaves, one is called small cell lung cancer because the cancer cells are really tiny and small in how they look. The second is the non-small cell lung cancer. That is, by far, the most common form of lung cancer.”
Would liquid biopsy replace tissue biopsies? “My hope would be yes. Right now, the test approved by the FDA is simply after a diagnosis has been made for non-small cell lung cancer patients. There is another trial going on right now that’s looking at early detection of tumors. For example, one of the reasons tumors are not detected early on is because they’re so tiny, they hide in the body. It’s difficult to find them unless they create a critical mass that shows up on an imaging study like a CT scan or a mammography machine. This test, if it is done the right way, has the potential not to just help with treatment decision making, but with early detection. It also offers an opportunity to monitor tumor response (more often). So, this test has the potential to replace a lot of other biopsies, a lot of other procedures.”
What does this mean for the patient? “Just imagine a woman did not have to go through a yearly mammogram. Just imagine a man did not have to go through a prostate exam once a year and could offer a blood sample to look at the cancer. Just imagine if someone did not have to go through a biopsy where a needle has to be placed inside the tumor, which has its own complications. Not just that, once a patient has been started on treatment, going through regular CT scans, which adds cost, radiation and inconvenience. A lot of benefits on the patient’s side if this (approved expanded use of liquid biopsies) ever sees the light of day.”
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